One of the key components of a computer system is a place to store data. Typically computer systems employ a number of storage means to store data for use by a typical computer system. One of the places where a computer can store data is in a disk drive which is also called a direct access storage device.
A disk drive or direct access storage device includes several disks which look similar to 45 rpm records used on a record player or compact disks which are used in a CD player. The disks are stacked on a spindle, much like several 45 rpm records awaiting to be played. In a disk drive, however, the disks are mounted to spindle and spaced apart so that the separate disks do not touch each other.
The surface of each disk is uniform in appearance. However, in actuality, each of the surfaces is divided into portions where data is stored. There are a number of tracks situated in concentric circles like rings on a tree. Compact disks have tracks as do the disks in a disk drive. The tracks in either the disk drive or the compact disk essentially replace the grooves in a 45 rpm record. Each track in a disk drive is further subdivided into a number of sectors which is essentially just one piece of the track.
Disks in a disk drive are made of a variety of materials. Most commonly, the disk is made of metal or plastic. The material from which the disk is made determines how data is stored on the disk. A plastic disk, such as those used as CD's, stores data using lasers and a laser is used to read the data back. Storage of data on a metal disk entails magnetizing portions of the disk in a pattern which reflects the data.
To store data on a metal disk, the metal disk is magnetized. In order to magnetize the surface of a disk, a small ceramic block which contains a magnetic transducer known as a read/write head is passed over the surface of the disk. More specifically, the read/write head is flown at a height of approximately six millionths of an inch from the surface of the disk and is flown over the track as the read/write head is energized to various states causing the track below to be magnetized to represent the data to be stored.
To retrieve data stored on a magnetic disk, the read/write head is flown over the metal disk. The magnetized portions of the disk induce a current in the read/write head. By looking at output from the read/write head, the data can be reconstructed and then used by the computer system.
Like a record, both sides of a disk are generally used to store data or other information necessary for the operation of the disk drive. Since the disks are held in a stack and are spaced apart from one another, both the top and the bottom surface of each disk in the stack of disks has its own read/write head. This would be comparable to having a stereo that could play both sides of a record at once. Each side would have a stylus which played the particular side of the record.
Disk drives also have something that compares to the tone arm of a stereo record player. The tone arm of a disk drive, termed an actuator arm, holds all the read/write heads, one head for each surface of each disk supported in a structure that looks like a comb. The structure is also commonly called an E block. Like a tone arm, the actuator arms rotate so that the read/ write heads attached to the actuator arm can be moved to locations over various tracks on the disk. In this way, the read/write heads can be used to magnetize the surface of the disk in a pattern representing the data at one of several track locations or used to detect the magnetized pattern on one of the tracks of a disk.
A shaft and a precision bearing set are attached to the actuator arm to provide for smooth rotational movement of the actuator arm. This particular invention deals with attaching the shaft and bearing to the actuator arm so that play in the actuator arm will be significantly lessened and so that the actuator arm will not be stressed resulting in the read/write heads being positioned out of alignment.
It is important to keep the read/write heads attached to the actuator arm aligned in a disk drive for the following reason. One of the ways to locate particular tracks is to make one surface of one disk a reference surface. Locational information is placed on the reference surface. All of the tracks at the same circumference are identified by referring to the locational information on the reference surface. If the read/write heads get out of alignment, the locational information on the reference surface may indicate that another read/write head is over a particular track when in fact it is over an adjacent track. The result would be that the wrong track may be magnetized or that the wrong track may be read resulting in retrieval of the wrong information. This would be similar to looking into the wrong mailbox and expecting to find your mail.
In the past a shaft and a bearing set were incorporated into the actuator arm. The shaft and bearings are typically made out of one material and the actuator arm is made out of another. When the shaft and bearings were incorporated into the actuator arm, the two materials would expand at different rates as the disk drive heated up during operation. Since the two materials were attached to one another and expanded at different rates, stresses resulted in the actuator arm which positioned the read/write heads out of alignment. An additional problem was that the spacing between the surfaces holding the individual bearings would change as the two materials would expand as the disk drive heated. The bearings would either be constricted so the bearings would bind, or the bearings would become a little looser resulting in less precision bearings.
To solve the problem of the spacing changes between the surfaces holding the bearings, a bearing cartridge was produced. The bearing cartridge includes an outer cylinder, the bearings and the shaft. The components of the bearing cartridge are made out of the same material so that as the bearing cartridge is heated, all of the materials expand at the same rate and the fits between the surfaces adjacent the bearings remain constant. Since the fits remain constant, the bearings do not become loose or become constricted. The attachment of the bearing cartridge to the actuator arm still resulted in the problems of stresses in the actuator arm causing the read/write heads to be positioned out of alignment. This particular invention discloses a method and apparatus for attaching the bearing cartridge to the actuator arm to eliminate or minimize the problem of stress buildup in the actuator arm resulting in misalignment of the read/write heads on the actuator arm.